Synthesis, Structure Characterization And Catalytic Activity Evaluation Of Ferrocene Phosphine-based Palladium(?) Complex As A Catalyst For Coupling Reaction

Palladium-ferrocenylphosphine complexes,as an important class of palladium-based molecular catalysts,exhibit excellent catalytic performance in the coupling reactions,due to a large steric hindrance of ferrocenylphosphine ligand which facilitates the reduction elimination step,and have been widely used in the fields of drug synthesis,natural product preparation and the production of organic opo-electronic material.Basing on the previous research reported in the literature,we have designed and developed a new synthetic technique for palladium-ferrocenylephosphine complexes,with an aim to improve and optimize the existing laboratory process.The target complexes were synthesized in batches from sodium tetrachloropalladate?II?,sodium tetrabromopalladate?II?or palladium?II?iodide as the palladium precursors,via ligand substitution reactions under an inert atmosphere.The batch quantity ranged from 20-250grams and high yields were achieved.The yield of 1,1-bis?diphenylphosphino?ferrocenepalladium?II?X₂ was found to be 92.4%?X=Cl?,80.0%?X=Br?and 75.3%?X=I?,whereas for 1,1-bis?di-tert-butylphosphine?ferrocenepalladium?II?X₂,the yield was 90.0%?X=Cl?,97.1%?X=Br?and 80.1%?X=I?.The target complexes were measured and characterized by different analytical techniques including ¹H NMR,mass spectra?MS?and single crystal X-ray diffraction analysis?XRD?,and related structural parameters were given for better understanding of their catalytic activity.Among fifteen synthesized complexes,four complexes?1,1-bis?diphenylphosphino?ferrocenepalladium?II?X2 and 1,1-bis?di-tert-butylphosphine?ferrocenepalladium?II?X2,X=Cl,Br?were selected for the evaluations of catalytic profile both in the three well-kunown coupling reactions?Suzuki,Sonogashira and Heck coupling reaction?and in the coupling reaction between 2-hydroxypyridine and boronic acid reagent,the halogenated aromatic and the aniline compound.The results show that four complexes are stable in a non-protective atmosphere and can efficiently catalyze a series of coupling reactions.More importantly,they display an excellent selectivity in catalyzing unilateral Sonogashira coupling reaction,presenting a good application prospect.